The invention generally refers to a force sensor for the measurement of axially occurring forces. It specifically refers to such a force sensor for which a measurement axis runs parallel to an axis of the force sensor.
For controlling or regulating a force, a force sensor is frequently used, which is arranged in the path of the force in such a way that the force to be adjusted acts on the sensor directly or indirectly through suitable means of transmission. Such devices are generally referred to as sensors, which qualitatively and quantitatively determine a measured value, in the present case a measured value associated with the force, and which transform this measured value into an electrical signal for further processing, so that it is available for the control or regulation of the force. Such force sensors are required for a variety of applications, such as for electromagnetic brakes within the automotive sector, for which the braking force, which acts upon the brake shoes, is determined and regulated by a force sensor.
Force sensors which are configured as a ring and which are configured on a shaft, axle, punch or any other cylindrical component that transmits the force are currently known as state of the art. Due to the diversity of applications of a force sensor, the ‘cylindrical’ shape of the component, which holds the ring-shaped force sensor, shall be known by its general definition, namely as a lateral surface, which is made up of a multitude of lateral lines, which connect the same two points of two identical, closed curves moved in parallel to each other along the length of the lateral line. The closed curves may be circles of a circular cylinder or ellipses of an elliptical cylinder or free curves. The ring-shaped force sensor is clearly adapted to the shape of the lateral surface.
As a result of the direct or indirect application of a force on the ring-shaped force sensor, the force sensor deforms, so that the to be measured force is deduced from the change in distance or length and the force is determined from the force-displacement-ratio. For instance in DE 103 50 085 A1, the control of the braking force of brake shoes are described. Therein, a circular ring-shaped force sensor, which has a C-shaped profile, is arranged on the casing of a compression die. The force, which is applied on the brake shoes through the compression die, acts in form of a reactive force of the brake shoes via suitable components of the brake on the force sensor and deforms the leg of a C-profile. Through strain measurements, the deformation of the ring and, thereof by means of a strain measurement system, the force acting on the brake shoes can be determined. Further areas of application for force sensors, which include a force ring, are known.